KR101727738B1 - Method and apparatus for transmitting packet in wireless communication system - Google Patents

Abstract

The present invention relates to a packet transmission method and apparatus in a wireless communication system.
According to another aspect of the present invention, there is provided a method of transmitting a packet in a wireless communication system, the method comprising: determining whether the packet is a response packet; And transmitting the packet with a higher channel access opportunity than another packet transmission apparatus of the wireless communication system when the packet is a response packet.
According to the present invention, in a wireless communication system using a fair competition-based channel access method, a packet transmission apparatus can not quickly receive a response packet even when a packet to be transmitted remains, Thereby solving the problem that the performance of the entire system deteriorates.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for transmitting packets in a wireless communication system,

The present invention relates to a packet transmission method and apparatus in a wireless communication system.

Referring to FIG. 1, the present wireless communication system has a structure in which one base station 100 communicates with one or more terminals 110-1,..., 110-n. For example, in a Code Division Multiple Access (CDMA) system, a base station communicates with one or more terminals in its zone. In an IEEE 802.11 wireless LAN system, a single access point : AP) communicates with one or more stations.

In this structure, a base station and one or more terminals access a channel through contention for channel occupancy and transmit a predetermined packet. In order to transmit packets in such a competitive wireless communication system, a method for improving the performance of the entire system becomes an issue.

In a wireless communication system using a fair competition-based channel access method, a packet transmission apparatus can not quickly receive a response packet even when a packet to be transmitted remains, And to provide a packet transmission method and apparatus in a wireless communication system that solves the problem that the performance of the entire system is degraded.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description and more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

According to an aspect of the present invention, there is provided a packet transmission method for a packet transmission apparatus in a wireless communication system, the method comprising: determining whether the packet is a response packet; And transmitting the packet with a higher channel access opportunity than another packet transmission apparatus of the wireless communication system when the packet is a response packet.

A packet transmission apparatus for transmitting a packet in a wireless communication system according to an embodiment of the present invention includes: a packet classification unit for determining whether the packet is a response packet; A transmitter for transmitting the packet; And a control unit for controlling the transmission unit to transmit the packet with a higher channel access opportunity than other packet transmission devices in the wireless communication system when the packet is a response packet.

According to the present invention, in a wireless communication system using a fair competition-based channel access method, a packet transmission apparatus can not quickly receive a response packet even when a packet to be transmitted remains, Thereby solving the problem that the performance of the entire system deteriorates.

1 is a diagram showing the structure of a wireless communication system.
2 is a flowchart illustrating a packet transmission method according to an embodiment of the present invention.
3 is a flowchart illustrating a packet transmission method according to another embodiment of the present invention.
4 is a diagram illustrating a configuration of a packet transmission apparatus according to an embodiment of the present invention.

The above and other objects, features, and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, which are not intended to limit the scope of the present invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote the same or similar elements.

1 is a diagram showing the structure of a wireless communication system. Referring to FIG. 1, a wireless communication system includes one base station (or access point) 100 and one or more terminals (or stations) 110-1,..., 110-n. Hereinafter, for convenience of description, the term IEEE 802.11 wireless LAN will be used. The present invention is not limited to terms such as an access point (AP) and a station.

In a wireless communication system, an access point and one or more stations compete for channel occupancy before transmitting a packet. For example, the IEEE 802.11 wireless LAN standard suggests a competition based on a random backoff scheme. The random backoff scheme generates an arbitrary slot time value within a specific range (e.g., a defined Contention Window value) before occupying the channel to transmit the generated packet, It is a method to start packet transmission when the channel is empty during the time.

In this way, when accessing a channel based on a contention, each station and an access point use the same contention window value, and thus transmit packets at the same probability. The station or access point that started the transmission may change the transmission rate according to the channel condition at the time of transmission. If the channel condition is not good and there are many errors, the transmission speed is lowered and the transmission speed is increased when the channel condition is good. This is because the modulation used for the low transmission rate requires a low signal-to-noise ratio (SNR) and the modulation used for the high transmission rate requires a high signal-to-noise ratio.

Thus, when all the stations and access points use channels fairly, there occurs a problem that the overall performance is deteriorated when the transmission speeds of the stations and the access points are different.

For example, if there is a station (STA1) with a speed of 1 Mbps and a station (STA2) with a speed of 11 Mbps, the two stations alternate (50% probability of accessing the channel) If it is transmitted, STA1 is transmitted for 11 seconds, and STA2 is transmitted for 1 second. That is, STA1 and STA2 have the same opportunity to access the channel, but the time to use the channel depends on the transmission rate. Ultimately, measuring the speed of packets transmitted globally in such a system would result in 22 megabits per second being transmitted every 12 seconds, resulting in a total performance of about 1.8 Mbps. A phenomenon in which a station having such a high transmission rate is degraded by a station having a low transmission rate is called a "performance anomaly".

If each station has the same transmission time when it gets a transmission opportunity once, the performance of the whole system can be greatly improved. For example, if STA1 transmits for 11 seconds and STA2 for 11 seconds, STA1 will send 1 packet on each transmission and STA2 will send 11 packets, so on the system-wide side, 22 seconds 11 * 1 + 11 * 11 = 132 Mega bits. This results in a performance improvement of 3.3 times that of 1.8 Mbps at a rate of about 6 Mbps.

In order to take advantage of the improved performance when each station that has the transmission opportunity is allowed to transmit all at the same time, IEEE 802.11e introduced the concept of TXOP (Transmit Opportunity). The station or access point that occupied the channel can continue to send packets without competing for the TXOP time, allowing stations with higher transmission speeds to send more packets.

The problem arises when it is possible to transmit the next packet only after waiting for a specific packet to be received from the destination after transmitting the packet in the upper layer and then receiving the specific packet.

An example of such a transmission scheme is TCP / IP, which is currently used in the transport layer. In order to guarantee the reliability of a packet, the TCP protocol transmits a packet, checks whether a transmitted packet arrives well, and transmits the next packet. For example, after the destination of the transmitted packet receives a response packet (ACK), it sends the next packet. Therefore, if a response packet is not received, even if there is a packet to be transmitted, the packet is not sent down to the lower layer.

In case of the UDP protocol, even if there is no response to the transmitted packet, the next packet is sent. However, even if UDP is used in the transport layer, there is a case where the application layer above the transport layer uses the above transmission method, for example, a traffic measurement utility program (for example, IX Chariot). The traffic measurement utility program generates and transmits a packet only when a packet transmission request packet is received in generating a packet at an application terminal. That is, the next packet is transmitted only when a specific packet is transmitted from the destination.

However, when such a transmission scheme is used, when a station occupies a wireless channel and has an opportunity to transmit a packet, it may happen that the TXOP time given to the station can not be fully utilized. If the TXOP time that is given to the user is not used all the time, the performance anomaly problem described above occurs and the performance degradation occurs. The reason why the station does not fully utilize the TXOP time given to it is as follows.

When there are multiple stations and all use the TCP protocol, each station transmits the next packet only after receiving ACK, which is a response packet to the transmitted packet. At this time, since the access point or station has the same channel access opportunity, the access point can not directly transmit the ACK to the station. In this case, although the station has a lot of packets to be transmitted, since the ACK is not received, the next packet can not be transmitted, and therefore, the TXOP of the station can not be used.

The present invention can solve the bottleneck due to the above-described response packet delay by providing a high priority to the response packet. As a result, when the station obtains the transmission opportunity, it can maximize the time allocated to the station, thereby improving the performance of the entire system. In other words, in the wireless communication system in which an access point and one or more stations have the same transmission opportunity, when using a transmission method of transmitting a next packet after receiving a response packet from a destination at a transport layer or an application layer, To a packet transmission method and apparatus capable of providing a packet.

Hereinafter, in a wireless communication system in which an access point and one or more stations have the same transmission opportunity, when a station uses a transmission method of transmitting a next packet after receiving a response packet from an access point, when an access point transmits a response packet As an example. On the contrary, it goes without saying that the present invention can be applied to a case where a station transmits a response packet when the access point uses a transmission method of transmitting a next packet after receiving a response packet from the station.

A packet transmission method according to an embodiment of the present invention will be described with reference to FIG.

In step S202, the access point 100 generates a packet to be transmitted. Referring to FIG. 1, for example, the access point 100 may generate a packet to be transmitted to the station 1 (110-1). At this time, the access point 100 may receive a packet from another station or a terminal on another network, and may generate a packet to be transmitted to the first station 110-1. Accordingly, the packet generated in step S202 may be a packet newly generated by the access point 100, a packet received from another station or a terminal on another network, Modified, and / or deleted packets.

In step S204, the access point 100 determines whether the packet to be transmitted is a response packet. The response packet may be a packet representing a response to a packet transmitted from the station or a packet for inducing a station to transmit a packet. For example, the response packet may be an ACK used in the TCP protocol or a packet transmission request packet used in the traffic measurement utility program. Hereinafter, a method for determining whether or not a packet is a response packet by classifying the packet will be described.

First, when the packet to be transmitted to the station 1 (110-1) includes information indicating whether the packet is a response packet (hereinafter referred to as 'response packet information'), the access point 100 It is possible to determine whether the packet is a response packet by using the response packet information. The response packet information may be included in the step S202 by the access point 100 or may be transmitted to the first station 110-1 through the access point 100 by a terminal in another station or another network .

In one embodiment, the response packet information may be included in a specific field of a header of the packet according to each protocol. In this case, the access point 100 can determine whether the corresponding packet is a response packet by using the information included in the specific field of the header of the packet according to each protocol. For example, if the value of the TYPE field in the header of the IP packet is "ACK ", the packet is determined to be a response packet.

In another embodiment, the response packet information may be included in an unused field (e.g., a reserved field) in the packet. At this time, it is also possible to display the response packet information in an unused field in the packet by using a table storing a criterion for classifying the packet. For example, if there is any value in any field of the header of the packet according to each protocol, response packet information may be displayed in an unused field in the packet by using a table storing information indicating whether the packet is a response packet . In this case, the access point 100 determines whether the packet is a response packet using the response packet information included in the unused field in the packet.

The second method will be described. First, the access point 100 identifies a source and a destination of a packet to be transmitted and received, sees the source and the destination as one pair, history information. Then, the history information on the number (X) of packets continuously transmitted in a specific destination direction from a specific source and the number (Y) of packets continuously transmitted in the specific source direction in the specific destination are analyzed. If Y packets go out every X packets in the opposite direction, the Y packets going out after the next X packets can be judged as response packets. For example, if one packet is transmitted from B to A for every 10 packets transmitted from IP 192.168.0.1 (hereinafter referred to as 'A') to IP 192.168.0.100 (hereinafter referred to as 'B'), One packet transmitted from B to A after 10 packets transmitted from B to A may be classified as a response packet.

If the packet to be transmitted is a response packet (S204: Yes), the access point 100 tries to transmit with a higher channel access opportunity than other stations (S206). At this time, if the channel is idle, the packet is transmitted. If the station transmits a response packet, the station may attempt to transmit with a higher channel access opportunity than the access point 100 and other stations. Hereinafter, a method of adjusting the channel access opportunity in step S206 will be described.

First, in the IEEE 802.11 MAC (Media Access Control), a channel access opportunity can be adjusted using a contention window value. The random backoff procedure used in IEEE 802.11 randomly generates a value between 0 and the contention window value, waits for a time corresponding to the generated number, and then tries to transmit. At this time, since the access point 100 and all the stations use the same contention window value, they try to transmit at the same probability. Therefore, if the value of the contention window is lowered, the probability that the number generated at random increases is increased, so that it is possible to have more transmission opportunities because the time to wait on the average is reduced. Therefore, the access point 100 may try to transmit using a lower contention window value than another station.

If a MAC other than the IEEE 802.11 MAC is used, the parameter for increasing the channel access probability in the MAC can be found and adjusted. Understanding the MAC protocol used in the system allows intuitively knowing which parameter increases the chance of channel access when adjusting the parameters, so the access point 100 can adjust the parameters and try to transmit.

If the packet to be transmitted is not a response packet (S204: NO), the access point 100 attempts transmission with the same channel access opportunity as another station (S208). At this time, if the channel is idle, the packet is transmitted. Similarly, when the station transmits a response packet, the station may attempt to transmit with the same channel access opportunity as the access point 100 and other stations.

Hereinafter, a packet transmission method according to another embodiment of the present invention will be described with reference to FIG. Here, the contents overlapping with those described in FIG. 2 will be omitted.

In step S302, the access point 100 generates a packet to be transmitted. This is described in step S202.

The access point 100 classifies the packet (S304), and determines whether the packet to be transmitted is a response packet (S306). A method of classifying a packet and determining whether it is a response packet is the same as that described in step S204.

If the packet to be transmitted is a response packet (S306: YES), the access point 100 stores the packet to be transmitted in a queue (hereinafter, 'response packet queue') (S308).

Then, at the time of packet transmission, it is determined whether there is a packet to be transmitted in the response packet queue (S310). If there is a packet to be transmitted in the response packet queue (S310: Yes), the access point 100 attempts to transmit a packet in the response packet queue with a higher channel access opportunity than other stations (S312). This is the same as described in step S206. If there is no packet to be transmitted in the response packet queue (S310: NO), the access point 100 attempts transmission with the same channel access opportunity as another station (S314). This is the same as that described in step S208.

In one embodiment, steps S302, S304, S306, and S308 may be performed in a layer higher than the MAC layer, and S310, S312, and S314 may be performed in the MAC layer. Layers higher than the MAC layer include the application layer, the transport layer, and the network layer.

In the case where the access point and one or more stations of the wireless communication system use the TCP protocol in the transport layer and the IEEE 802.11 MAC is used in the MAC layer, the embodiment of FIG. 3 will be described. First, it is assumed that there are packets to be transmitted to the access point 100 by the ten stations 110-1, 110-2, ..., 110-10. A station of a station 1 (110-1) to a station 10 (110-10) transmits a packet by a random backoff procedure defined in IEEE 802.11. The channel access method by the Random back off procedure is such that all the stations access the channel with the same probability. Therefore, after a certain time, every station transmits one or more packets. Since all stations use TCP in the transport layer, the access point 100 must transmit an ACK for the packets transmitted by all the stations. At this time, the access point 100 classifies the ACK into a response packet by the packet classification process shown in the present invention and stores it in the response packet queue. Thereafter, the access point 100 makes a transmission attempt with a high channel access opportunity to the ACK stored in the response packet queue.

Hereinafter, a packet transmission apparatus according to an embodiment of the present invention will be described with reference to FIG. The packet transmission device refers to a device that transmits a packet in a wireless communication system, and may be, for example, an access point and a station. Here, the contents overlapping with those described in FIG. 2 and FIG. 3 will be omitted.

The packet transmission apparatus 400 may include a packet classification unit 420, a control unit 430, and a transmission unit 440.

The packet classifying unit 420 determines whether the packet to be transmitted is a response packet. A method of classifying a packet and determining whether it is a response packet is the same as that described in step S204. 3, when the packet to be transmitted is a response packet, the packet classifying unit 420 may store a packet to be transmitted in a response packet queue.

The transmitting unit 440 transmits a packet to be transmitted through a channel.

If the packet to be transmitted is a response packet, the control unit 430 tries to transmit with a higher channel access opportunity than other stations, and if the packet to be transmitted is not a response packet, the control unit 430 tries to transmit the same channel access opportunity with another station , And controls the transmitting unit 440. This is as described in steps S206, S208, S310, S312, and S314.

The packet transmission apparatus 400 may further include a packet generation unit 410. The packet generation unit 410 generates a packet to be transmitted. This is described in step S202.

400: Packet transmission apparatus 410: Packet generation unit
420: packet classifying unit 430:
440:

Claims (14)

A method for transmitting a packet in a wireless communication system, the method comprising:
Determining whether the packet is a response packet; And
When the packet is a response packet, transmitting the packet with a higher channel access opportunity than another packet transmission device in the wireless communication system
/ RTI >
Wherein the step of determining whether the packet is a response packet comprises the steps of: determining a first number of packets continuously transmitted from a source to a destination and a second number of packets continuously transmitted from the destination to the source The second number of packets successively transmitted from the destination to the source after the first number of packets continuously transmitted from the source to the destination is determined as a response packet,
A method of transmitting a packet in a wireless communication system.
The method according to claim 1,
When the packet is not a response packet, transmitting the packet with the same channel access opportunity as another packet transmission apparatus of the wireless communication system
And transmitting the packet to the base station.
The method according to claim 1,
Wherein the step of determining whether the packet is a response packet includes a field indicating whether the packet is a response packet or not,
A method of transmitting a packet in a wireless communication system.
delete The method according to claim 1,
Further comprising: if the packet is a response packet, storing the packet in a queue,
Wherein transmitting the packet with a higher channel access opportunity than other packet transmission devices in the wireless communication system is performed when a packet is present in the queue.
A method of transmitting a packet in a wireless communication system.
The method according to claim 1,
Wherein the step of transmitting the packet with a higher channel access opportunity than another packet transmission device of the wireless communication system comprises:
And transmits the packet using a lower contention window value than another packet transmission apparatus of the wireless communication system.
A method of transmitting a packet in a wireless communication system.
3. The method of claim 2,
Wherein the step of transmitting the packet with the same channel access opportunity as another packet transmission apparatus of the wireless communication system comprises:
And transmits the packet using the same contention window value as another packet transmission apparatus of the wireless communication system.
A method of transmitting a packet in a wireless communication system.
A packet transmission apparatus for transmitting a packet in a wireless communication system,
A packet classifying unit for determining whether the packet is a response packet;
A transmitter for transmitting the packet; And
When the packet is a response packet, controls the transmission unit to transmit the packet with a higher channel access opportunity than another packet transmission apparatus of the wireless communication system,
/ RTI >
Wherein the packet classifier comprises:
Analyzing a history of a first number of packets continuously transmitted from a source to a destination and a second number of packets continuously transmitted to the source at the destination, The second number of packets continuously transmitted from the destination to the source is determined as a response packet after the first number of packets to be transmitted,
A packet transmission device in a wireless communication system.
9. The method of claim 8,
Wherein,
When the packet is not a response packet, controls the transmission unit to transmit the packet with the same channel access opportunity as another packet transmission apparatus of the wireless communication system
A packet transmission device in a wireless communication system.
9. The method of claim 8,
When the packet includes a field indicating whether the packet is a response packet, the packet classifying unit determines whether the packet is a response packet through the field,
A packet transmission device in a wireless communication system.
delete 9. The method of claim 8,
Wherein the packet classifier stores the packet in a queue when it is determined that the packet is a response packet,
The control unit controls the transmission unit to transmit the packet with a higher channel access opportunity than other packet transmission devices in the wireless communication system when the packet exists in the queue
A packet transmission device in a wireless communication system.
9. The method of claim 8,
Wherein,
And controlling the transmitter to transmit the packet using a contention window value lower than that of another packet transmission apparatus of the wireless communication system when the packet is a response packet,
A packet transmission device in a wireless communication system.
9. The method of claim 8,
Wherein,
And controlling the transmitter to transmit the packet using the same contention window value as another packet transmission apparatus in the wireless communication system when the packet is not a response packet,
A packet transmission device in a wireless communication system.

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